EDIT: I believe I have kicked a hornet’s nest. Did not expect this to blow up! But I am still looking for the “ur time”. the basis for it all. Like, maybe the big bang, or something.
In: 5399
Fun fact: Chances are, you’ve never in your life cared about your true local time. You think your local time is based on your time zone. Unless you’re really, really lucky though your timezone won’t give you the “correct” time based on your exact location – it’s an approximation for a given geographic area. Your “true” local time would be best measured by setting noon to when the sun is at its highest elevation each day.
Edit: Might as well share some of my other “Astro” related knowledge. On my first deployment with the Navy, I spent most of the 6-month trip filling the role of “Astro boy”. I had to do all the Astro calculations for each day. This was back before the internet or an app could do it for you. I’d calculate:
* Sunrise/Sunset (Sun halfway above the horizon)
* Civil Morning/Evening Twilight (Center of the sun’s disk 6 degrees below the horizon)
* Nautical Morning/Evening Twilight (Center of the sun’s disk 12 degrees below the horizon)
* Bearing Amplitude of the Sun/Moon (The compass bearing where the sun/moon rises/sets)
* And just for kicks and to prove how precise my calculations were, True Local Time. Which in a moving ship, also requires you to extrapolate your position at noon accurately.
Much like True Local Time, most people don’t think about bearing amplitude of the sun/moon. You think the sun rises in the east and sets in the west. That’s generally true, but not very accurate. If you’re well north of the equator, the sun will rise and set south of a perfect east/west heading, and vice versa if you’re south of the equator. Once upon a time, mariners would use bearing amplitude to check and calibrate their navigation equipment. By the time we started using laser ring gyros, Radio Aids to Navigation, Inertial navigation systems, and GPS, it was more just a way to torture junior officers.
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